April 15, 2013 / Vol. 38, No. 8 / OPTICS LETTERS 1259 Silicon optical diode with 40 dB nonreciprocal transmission Li Fan,* Leo T. Varghese, Jian Wang, Yi Xuan, Andrew M. Weiner, and Minghao Qi Birck Nanotechnology Center and School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA *Corresponding author:
[email protected] Received January 23, 2013; revised February 28, 2013; accepted March 8, 2013; posted March 13, 2013 (Doc. ID 182747); published April 4, 2013 A passive all-silicon optical diode is demonstrated to realize a record high nonreciprocal transmission ratio (NTR) of 40 dB. Individual microrings that make up the device are experimentally studied to explain the nonlinear power dynamics. There is a compromise between the NTR and insertion loss, and possible solutions for further improve- ments are discussed. This work provides a way to realize extremely high optical nonreciprocity on chip for optical information processing applications. © 2013 Optical Society of America OCIS codes: 230.5750, 230.3120. Optical nonreciprocity (ONR) for on-chip information While no overcladding is used, SU8 resist is patterned processing is highly desirable but has yet been elusive over the vertical grating couplers to efficiently couple due to material and fabrication challenges. A number TM light in and out of the two ports with a fiber–chip– of ideas based on magneto-optic effect [1–5], indirect in- fiber loss of 13 dB at 1580 nm. All power values are cal- terband photonic transition [6,7], and electro-absorption culated at the device, by assuming the input and output modulation [8] have been investigated, with various lev- grating couplers have identical loss.